


Best Mate's Brother And Brother's Boyfriend

by camichats



Series: Imagine James and Sirius Prompts [33]
Category: Harry Potter - J. K. Rowling
Genre: Alternate Universe, Alternate Universe - No Voldemort, Fake James/Regulus, Getting Together, M/M, Marauders' Era, Misunderstandings, Slytherin James, Sneaky Regulus
Language: English
Status: Completed
Published: 2018-01-07
Updated: 2018-01-07
Packaged: 2019-03-01 13:51:14
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,178
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13296222
Author URL: https://archiveofourown.org/users/camichats/pseuds/camichats
Summary: James is pining over Sirius from afar, and Regulus is Done.





	Best Mate's Brother And Brother's Boyfriend

**Author's Note:**

> I feel like this is more Regulus-is-James's-best-friend AU than anything else, but uh, here we are. 
> 
> For the prompt: “Could you write a fic where James is a Slytherin please? I can't get the idea out of my head.”
> 
> Originally posted on [tumblr](https://imaginejamesandsirius.tumblr.com/post/169404598245/could-you-write-a-fic-where-james-is-a-slytherin)

James sighed-- for the fourth time that morning-- and Regulus put his fork on the table forcefully, making it click against the wood of the table, which he normally never would do. “Stop that.”

“Stop what?” James asked even though he knew exactly what Reg was talking about.

“Can’t you pine elsewhere? I’m trying to have a nice breakfast here.”

James made eye contact with him and sighed again, laughing when Regulus glared at him and fingered his utensil threateningly. “He’s so gorgeous.”

Regulus scrubbed at his face, then dragged his hands down. “You’re driving me mad with this. Go up to _him_ and wax poetic about his good looks, I’m sure he’d appreciate it.”

“I tried that once-” in third year on Valentine’s day “-and it didn’t end well, you might recall.”

“He thought you were mocking him! That’s all you did back then. Now that you’re older and,” Regulus wrinkled his nose as if saying the next word pained him, “wiser, it won’t go the same.”

James raised an eyebrow at him. “You want me to date your brother?” he asked disbelievingly.

“What I _want_ is for you to shut it so I can do things in peace. Eat, read, study, enjoy the weekend, virtually _everything,_ without you sighing all dramatically in my ear.”

James put his arm over Regulus’s shoulders, making him peer at James suspiciously.

“What are you--” James put his face close to his ear and took a deep, loud breath in. Regulus shoved him off before he could do anything else. “For Salazar’s sake! Go make yourself another friend and leave me alone for an hour.”

“Classes are starting soon, you’ll have the rest of your day in peace.” Or most of it, until supper.

“Not soon enough,” he grumbled, turning back to his breakfast. “Go ask out my brother or leave.”

James did neither, but he stayed quiet so Reg was fine with it. James would certainly ask Sirius out if he thought he’d say yes. As it stood, he was more likely to receive a hex to the face than an acceptance.

* * *

James tried to psych himself up to talk to Sirius-- not even asking him for a date, just talking-- but he chickened out every time. No wonder he didn’t get put in Gryffindor.

Fate, as it turned out, wasn’t willing to see him continue on like this because one day he was leaning against a wall outside looking at the Quidditch pitch when Sirius came out and joined him. James didn’t bother trying to hide how shocked he was. “Er, you alright there?”

“‘Course,” Sirius said, looking for all the world as if they did this all the time. “Why? Have I got something on my face?”

James spluttered, personally offended that someone-- even Sirius himself-- would say that. “ _No_ ,” he managed.

Sirius blinked at him. “Okay.” He peered at him for a moment before saying, “Reg was talking to me about you, y’know. Little bugger wouldn’t shut it about how great you are, begged me to give you half a chance. And also said that you’re coming to ours for part of break, apparently, but,” he shrugged.

“O… kay.” Regulus had made no such plans with him, but he would deal with that later. Sirius was going to give him a chance? “Is that what this is?” James would have preferred being cornered in the library or summat, but he wasn’t going to complain about the specifics of finally having a civil conversation with the man. Even if it could have been warmer.

“Not really.”

“Oh.” James deflated. “Then what is this?”

Sirius turned to face him completely, his leather covered shoulder leaning against the wall of the castle. How dare he wear that sodding jacket to talk to James. How _dare_ he. No one could look that good and expect everyone else to be fully in charge of their faculties. James had been able to ignore it earlier because 1. He was surprised and 2. Sirius hadn’t been facing him-- he hadn’t gotten a good look.

“This is me telling you that you better not hurt him.”

“What?”

Sirius sighed, running a hand through his stupid perfect hair. “Reg and I haven’t had the best relationship in the past, and I’m trying to get better about that. Threatening his boyfriend won’t get me in his good graces, but,” he shrugged again. “He’s a lot softer than he lets on, and a bit naive when it comes to shite like this. So. Treat him right, and as long as you don’t purposefully bugger up, we won’t have a problem. Alright, Potter?”

James’s mind had stalled out on ‘boyfriend’ so he just said, “What?” again. What the bloody hell had Reg told him and _why_?

Sirius rolled his eyes and pushed himself away from the wall in a fluid motion. “Merlin only knows what that boy sees in you.”

James didn’t visibly flinch, but Godric and Salazar did he want to. That had _not_ been a teasing tone; Sirius legitimately didn’t understand why someone would want to spend time with him. “Yeah, well it doesn’t rightly matter what you think, does it? He can make his own decisions, and like you said, you haven’t exactly had the best relationship,” James said. He didn’t really _mean_ for it to be a cutting remark, but that’s definitely how it came out. It also made Sirius’s eyes harden into something distinctly hostile before he left, sending a v back at James.

Great.

* * *

“I’m going to yours for break?” James asked.

Regulus blinked up at him, quill poised over his assignment. “Ah.” He put his quill down and leaned back in his chair. “I see Sirius talked to you then?”

“Yes. Would a warning have been too much for you?”

Regulus rolled his eyes. “It got the two of you talking. You’re welcome, by the way.”

“I’m not thanking you; this is a sodding disaster.”

He sighed. “You’re just as melodramatic as he is.”

James thought that was rich, coming from him. Apparently this was going to be a long conversation, so he sat across from him, moving a pile of books on the table with a raised eyebrow; Reg wouldn’t be able to use all of these in one sitting. “He threatened me.”

Regulus frowned. “Really?”

“Yeah. Granted it was conditional on me hurting you, but still. Did you know he thinks you’re innocent and naive?”

“Unfortunately,” he said, not sounding the least bit surprised. “We’ve been friends for years, why is he worried all of a sudden? If anything, you’re safer now than you were six years ago.”

James had the worst sense of foreboding, but he had to confirm it. “He thinks we’re dating,” he explained slowly.

“He _what_?!”

“You didn’t tell him that?”

“No!” He winced, remembering they were in the library. “Why does he think we’re dating?”

“I guess you said too many nice things about me.” Regulus was gaping at him, but fuck if James knew what to do. He just shrugged. “So am I actually going to yours or no?”

“Hm? Oh, yes. It wasn’t supposed to go like this, but my parents agreed, which is something of a miracle, I doubt they’ll do it twice.”

“How was it supposed to go?” James asked suspiciously. He loves Reg-- really, he does-- but any time that boy plotted on his own, James ended up in the Blast Ended Skrewts’ pen.

Regulus blinked at him innocently. “I should really get back to work.” With that, he picked up his quill and ignored James entirely. James tried to stare him into explaining, but Reg was much better at ignoring him than James was at being ignored. After a few minutes, he gave up and left.

* * *

Walburga looked at him like he was the scum in her walkway, and James made a point to smile sunnily, combating every backhanded comment with peppiness about his parents’ and his own accomplishments-- none of which she approved of, obviously.

Fortunately for everyone, she and Orion left for France after two days.

“What are the chances they’ll die over there?” James asked as soon as they flooed away. Sirius snorted in amusement, but Reg was looking at him in disapproval. “What? Oh come on, you can’t tell me you’d be broken up about it if they did.”

“James.”

He rolled his eyes. “You like them as much as I do, and we all know it.”

Reg stormed off though, so maybe that wasn’t true. In James’s defense, he _really_ hadn’t thought Regulus was upset.

“Smooth,” Sirius said.

James glared at him even though he was thinking the same thing. The point was that he and Sirius were not mates, and only mates were allowed to say shite like that. Not that Reg ever did, but it was the principle of the matter; Sirius wasn’t allowed.

After a few moments of James miserably looking at where Regulus had left, Sirius sighed. “He thinks he _should_ be upset with you about this, so he’s pretending to be. Cheer up love, by tonight you’ll be back in the honeymoon phase.”

James stared at him blankly as he-- there was no other word for it-- flounced out of the room. “What the fuck,” he whispered.

First of all, who called their brother’s boyfriend ‘love’? That they weren’t actually dating was immaterial, Sirius thought they were.

Second of all, who called it the honeymoon phase when they hadn’t just gotten together and were in nothing resembling a honeymoon phase?

 _Third_ of all, bugger Sirius and his- his fucking everything.

* * *

A few days later and Reg was still giving him the cold shoulder, making James feel inexplicably like they were in a toxic straight relationship where Regulus wouldn’t tell him what was wrong because he felt James should know and was just waiting for him to apologise profusely.

It was strange, but not near as strange as Sirius’s behaviour. He was… spending time with James. They played Exploding Snap and Gobstones and got halfway through a game of chess before they got bored and enchanted the pieces to mutiny against their king and queen. The pieces lived in peace for a while, until the pawns decided they didn’t like being talked down to and killed the ruling class. James and Sirius both watched it happen with morbid fascination, lifting the enchantment after their success before the remaining pawns and rooks could decide they didn’t like the humans controlling them.

They played more Snap and listened to the radio, singing along with what came on, making a contest of who could be more obnoxious about it. It was a tie.

“I don’t know what Reg sees in you,” Sirius said, both of them laid on their stomachs as they played a much more timid game of chess, but it was a far cry from the venomous way he’d said it that first time.

That didn’t stop James from being offended though. “Sod off, I’m a catch.”

“‘Course you are,” Sirius agreed easily-- which, _what_. “Doesn’t make you his type.”

“And you know what his type his?”

Sirius raised an eyebrow, which, while proving nothing, had the effect of making James feel like an idiot for asking.

James huffed. “Whatever, we’re not dating anyways.”

“What?”

“We’re not dating,” he repeated.

Sirius opened his mouth, then closed it without saying anything. He stared at James a little longer before groaning and dropping his head forward onto the floor.

“What?” James asked, alarmed.

“Reg is a little shit.”

“I mean, yeah. Why, though?”

Sirius lifted his head. “Making me think you two are dating? Inviting you over only to ignore you over something he doesn’t give a shite about?”

“I don’t know where you’re going with this,” James said. He knew how those things affected him and his feelings for Sirius-- aka he would marry him right here and now if he thought he’d say yes-- but what would they be doing to Sirius?

Sirius waved a hand to the side. “Oh you know, the whole me wanting to shag your brains out thing that dear Reggie is trying to bring to fruition.”

James felt heat rise in his face, but he couldn’t bring himself to stop looking at Sirius. Regulus was a dirty, dirty liar, and much better at it than James had thought. “Er,” he laughed nervously, “I thought you hated me?”

Sirius gave him a flat look. “I hated the idea that you were dating my brother. I’ve been trying to get your attention all this year, you berk. Besides, what the hell do you think the last couple days were?”

“I- well I dunno. My brain isn’t working right now.”

“Is your brain ever working?” Sirius teased.

“You’re the one who said you wanted to shag my brains out. It’s not my fault the suggestion of it started the process.”

Sirius smirked, looking entirely too self-satisfied. “That so?”

James hummed noncommittally. “You should get on with it so I can return the favour.”

“Well, since you asked so nicely…”

**Author's Note:**

> This is from a prompt driven blog @[imaginejamesandsirius](https://imaginejamesandsirius.tumblr.com) on tumblr. Feel free to send in a prompt of your own!


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